/etc/infiniband/openib.conf contains MLX4_LOAD=yes (as installed by sys-infiniband/ofed-3.5), but this is not obeyed by /etc/init.d/openib. I have to manually load the mlx4_ib module before starting openib. The init script should IMO either ignore all <MODNAME>_LOAD variables in /etc/infiniband/openib.conf (and let /etc/init.d/modules deal with those), or honor all of them.